Partial removal of the insulator on an electric conductor has often been practiced for the purpose of exposing the electric conductor in a terminal. A technique thereby employed is to paste a punched-out insulating film on the electric conductor and pattern the electrically conducting portion. Another technique is to remove the insulator underneath the patterned electric conductor by a special chemical [Japan Kokai Tokkyo Koho No. Sho 52-22071 (1977)] or by laser [Japan Kokai Tokkyo Koho No. Sho 62-22071 (1987)]. The former technique, based on fabrication by punching, poses problems of difficulties in attaining accuracy and also of expenditure for molds. On the other hand, the latter technique requires hazardous chemicals such as strong alkali and costly equipment for generation of laser and plasma and also poses the problem of low productivity.
An HDD (hard disk drive) suspension has been prepared by etching a stainless steel foil and a thin-film magnetic head is mounted on the tip of the suspension and packaged by wire bonding with a gold wire. A general structure of such HDD suspension is described in PETEROTECH, Volume 18, Number 11, page 351.
In recent years, however, active studies directed to smaller size and higher density and capacity of HDD suspensions are under way and the indispensable theme of such studies is low rise of suspensions (sliders). From this viewpoint, the conventional gold wire is an obstacle to low rise and, in addition, its resistance to air flow is detrimental to high-speed manufacture.
To solve the problem in question, an attempt has been made to form patterns of insulating polyimides directly on a stainless steel foil and then form a copper ciurcuit on the polyimides as disclosed in Japan Kokai Tokkyo Koho No. Sho 60-246015 (1985).
A technique such as this, however, still faces difficulties in forming a fine circuit. There are also problems, although latent, such as poor adhesion of polyimides to the substrate stainless steel foil and a long period of time, too long for an operation on an industrial scale, required for alkali etching of polyimide precursors.
An object of this invention is to provide laminates of high reliability and fabrication accuracy and excellent workability which allow the preparation of circuit boards by fabrication of the insulator.
Another object of this invention is to provide laminates of high reliability and fabricability useful for the preparation of HDD suspensions.